Mediterranean monk seals: biology

The monk seal family
Monk seals are pinnipeds (meaning "fin-footed") - a group of marine mammals with front and hind flippers that includes seals, sea lions, and walruses. Monk seals are "true" seals (family phocid), a subgroup of pinnipeds characterized by small flippers and ear holes with no external ear flaps. On land, phocids move by flopping along on their bellies, while at sea they swim by moving their back flippers like a fish tail.

Going two steps further down the pinniped family tree, monk seals belong to the Monachus genus, which has 3 species: the Mediterranean monk seal (Monachus monachus), the Hawaiian monk seal (M. schauinslandi), and the Caribbean monk seal (M. tropicalis), which became extinct in 1952.

Hawaiian monk seals are classified as endangered, and Mediterranean monk seals are classified as critically endangered.

Long whiskers and large black eyes
Both male and female adult Mediterranean monk seals are 2-3m in length and weigh approximately 200-300kg. Males range in colour from very dark brown to almost black, with a white patch on the belly. Females are light brown or grey, with a lighter or white belly from the throat to tail.

Newborn pups are about 80-90cm in length and weigh almost 20kg. Pups are born with longish black fur and a white patch on the belly. At two months of age, their coat begins to be replaced with shorter grey fur.

A seafood diet
Like other pinnipeds, Mediterranean monk seals are carnivores. They dive for fish, octopus and shellfish, staying under water for around 5-10 minutes before coming back to the surface for air. Compared to other pinnipeds, they are shallow divers, never going deeper than 100m. They eat the equivalent of 5% of their body weight each day - that's 18kg of fish for a full-grown seal!

Living in remote areas
Mediterranean monk seals prefer to live on quiet coastlines away from human disturbance. Their primary habitat is rocky areas with caves, but they will visit beaches and river mouths for hunting or when searching for a mate. As a large mammal with a healthy appetite, they need large areas in which to live. They cannot survive if restricted to one or two small bays, and need caves for giving birth and raising pups.

Shy and mostly solitary
Although they once lived in colonies (and still do on the Sahara coast of West Africa), hunting by humans has made Mediterranean monk seals more timid and less sociable than other pinnipeds. In the Mediterranean they have been observed in groups of 2-4, and rarely larger groups of up to 8, but are often solitary.

They may periodically gather together at certain times of the year, such as for breeding, and then disperse. Adult males are generally territorial and live in one area, while females are more nomadic. They are scattered along remote coastlines and islands with caves, where they shelter and give birth.

Starting out life in a cave
In the Mediterranean, whelping (giving birth) only occurs in caves. Female seals choose caves with distinct characteristics, such as a large size that provides shelter against harsh weather conditions, and a ledge on which they and the pups can rest.

In the first 6 months of a pup's life, small groups of monk seals form in and around the breeding cave. Here exploration, training, and social bonding of pups and juvenile monk seals takes place. Monk seals are most vulnerable to any form of human disturbance during their first 6 months of life.

This age group is most affected by entanglement and drowning in fishing gear. Protection of breeding caves and the open water around them is of primary importance for the survival of Mediterranean monk seals.